The long term objective of this proposed project is to discover which parts of the visual system are affected in patients with Alzheimer's Disease (AD); particularly those with severe and often disabling disturbances of visual perception. It is proposed to investigate the visual system by means of objective, noninvasive testing utilizing Visual Evoked Potentials (VEP) in patients with AD, together with age- matched controls, using recently developed computer generated visual stimuli that can relatively separate the function of several of the underlying multiple parallel processing systems in vision. Specific Aim (1) is to answer a number of questions about the visual deficits of a large cohort of AD patients and controls participating in an ongoing study (NIA, 1RO1 AG08870, "The Neuropsychology of Perceptual Disorders in Dementia"). Using appropriate visual stimuli, it is proposed to elicit neural responses from the magnocellular and parvocellular pathways, the "on" and "off" pathways, and the lateral inhibitory pathways; and to also test the synchronization of visual cortical input to bright flash stimulation of the retina. Specific Aim (2) is to correlate these results with those of the extensive physiological and behavioral studies which will have been performed upon this cohort of AD patients and controls. Specific comparisons will be made between the magnocellular/parvocellular results obtained in this proposed study, with the results of psychophysical probes of the magnocellular/parvocellular systems in the cohort.